Add fourth example

This commit is contained in:
Timothy Warren 2019-03-13 09:33:34 -04:00
parent c099c74f2e
commit 72d51250c2
5 changed files with 242 additions and 0 deletions

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//! # A Bad Stack
use std::mem; use std::mem;
pub struct List { pub struct List {

238
src/fourth.rs Normal file
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//! # A Bad Safe Deque
use std::rc::Rc;
use std::cell::{Ref, RefCell, RefMut};
pub struct List<T> {
head: Link<T>,
tail: Link<T>,
}
type Link<T> = Option<Rc<RefCell<Node<T>>>>;
struct Node<T> {
elem: T,
next: Link<T>,
prev: Link<T>,
}
pub struct IntoIter<T>(List<T>);
impl<T> Node<T> {
fn new(elem: T) -> Rc<RefCell<Self>> {
Rc::new(RefCell::new(Node {
elem,
prev: None,
next: None,
}))
}
}
impl<T> List<T> {
pub fn new() -> Self {
List {
head: None,
tail: None,
}
}
pub fn push_front(&mut self, elem: T) {
let new_head = Node::new(elem);
match self.head.take() {
Some(old_head) => {
old_head.borrow_mut().prev = Some(new_head.clone());
new_head.borrow_mut().next = Some(old_head);
self.head = Some(new_head);
}
None => {
self.tail = Some(new_head.clone());
self.head = Some(new_head);
}
}
}
pub fn pop_front(&mut self) -> Option<T> {
self.head.take().map(|old_head| {
match old_head.borrow_mut().next.take() {
Some(new_head) => {
new_head.borrow_mut().prev.take();
self.head = Some(new_head);
}
None => {
self.tail.take();
}
}
Rc::try_unwrap(old_head).ok().unwrap().into_inner().elem
})
}
pub fn push_back(&mut self, elem: T) {
let new_tail = Node::new(elem);
match self.tail.take() {
Some(old_tail) => {
old_tail.borrow_mut().next = Some(new_tail.clone());
new_tail.borrow_mut().prev = Some(old_tail);
self.tail = Some(new_tail);
}
None => {
self.head = Some(new_tail.clone());
self.tail = Some(new_tail);
}
}
}
pub fn pop_back(&mut self) -> Option<T> {
self.tail.take().map(|old_tail| {
match old_tail.borrow_mut().prev.take() {
Some(new_tail) => {
new_tail.borrow_mut().next.take();
self.tail = Some(new_tail);
}
None => {
self.head.take();
}
}
Rc::try_unwrap(old_tail).ok().unwrap().into_inner().elem
})
}
pub fn peek_front(&self) -> Option<Ref<T>> {
self.head.as_ref().map(|node| {
Ref::map(node.borrow(), |node| &node.elem)
})
}
pub fn peek_front_mut(&mut self) -> Option<RefMut<T>> {
self.head.as_ref().map(|node| {
RefMut::map(node.borrow_mut(), |node| &mut node.elem)
})
}
pub fn peek_back(&self) -> Option<Ref<T>> {
self.tail.as_ref().map(|node| {
Ref::map(node.borrow(), |node| &node.elem)
})
}
pub fn peek_back_mut(&mut self) -> Option<RefMut<T>> {
self.tail.as_ref().map(|node| {
RefMut::map(node.borrow_mut(), |node| &mut node.elem)
})
}
pub fn into_iter(self) -> IntoIter<T> {
IntoIter(self)
}
}
impl<T> Drop for List<T> {
fn drop(&mut self) {
while self.pop_front().is_some() {}
}
}
impl<T> Iterator for IntoIter<T> {
type Item = T;
fn next(&mut self) -> Option<T> {
self.0.pop_front()
}
}
impl<T> DoubleEndedIterator for IntoIter<T> {
fn next_back(&mut self) -> Option<T> {
self.0.pop_back()
}
}
#[cfg(test)]
mod test {
use super::List;
#[test]
fn basics() {
let mut list = List::new();
// Check empty list behaves right
assert_eq!(list.pop_front(), None);
// Populate list
list.push_front(1);
list.push_front(2);
list.push_front(3);
// Check normal removal
assert_eq!(list.pop_front(), Some(3));
assert_eq!(list.pop_front(), Some(2));
// Push some more just to make sure nothing's corrupted
list.push_front(4);
list.push_front(5);
// Check normal removal
assert_eq!(list.pop_front(), Some(5));
assert_eq!(list.pop_front(), Some(4));
// Check exhaustion
assert_eq!(list.pop_front(), Some(1));
assert_eq!(list.pop_front(), None);
// ---- back -----
// Check empty list behaves right
assert_eq!(list.pop_front(), None);
// Populate list
list.push_back(1);
list.push_back(2);
list.push_back(3);
// Check normal removal
assert_eq!(list.pop_back(), Some(3));
assert_eq!(list.pop_back(), Some(2));
// Push some more just to make sure nothing's corrupted
list.push_back(4);
list.push_back(5);
// Check normal removal
assert_eq!(list.pop_back(), Some(5));
assert_eq!(list.pop_back(), Some(4));
// Check exhaustion
assert_eq!(list.pop_back(), Some(1));
assert_eq!(list.pop_back(), None);
}
#[test]
fn peek() {
let mut list = List::new();
assert!(list.peek_front().is_none());
assert!(list.peek_back().is_none());
assert!(list.peek_front_mut().is_none());
assert!(list.peek_back_mut().is_none());
list.push_front(1);
list.push_front(2);
list.push_front(3);
assert_eq!(&*list.peek_front().unwrap(), &3);
assert_eq!(&mut *list.peek_front_mut().unwrap(), &mut 3);
assert_eq!(&*list.peek_back().unwrap(), &1);
assert_eq!(&mut *list.peek_back_mut().unwrap(), &mut 1);
}
#[test]
fn into_iter() {
let mut list = List::new();
list.push_front(1);
list.push_front(2);
list.push_front(3);
let mut iter = list.into_iter();
assert_eq!(iter.next(), Some(3));
assert_eq!(iter.next_back(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next_back(), None);
assert_eq!(iter.next(), None);
}
}

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pub mod first; pub mod first;
pub mod second; pub mod second;
pub mod third; pub mod third;
pub mod fourth;

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//! # An Ok Stack
pub struct List<T> { pub struct List<T> {
head: Link<T>, head: Link<T>,
} }

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//! # A Persistent Stack
use std::rc::Rc; use std::rc::Rc;
pub struct List<T> { pub struct List<T> {